Despite their primarily vegetarian diet, the world's third-largest land mammal is extremely aggressive and territorial and the combination of sheer size (males average 3,300 lbs), sharp teeth, and mobility both in and out of water make for a fearsome beast.

They are usually found in Sub-Saharan Africa, where they wallow in rivers and wetlands.

But, imported from a California zoo into Colombia by Pablo Escobar, they also appear to relish life in the wild in Latin America.

The Nile crocodiles, lions and hyenas which would prey on young hippos are not present in Colombia, meaning the population can grow unchecked.

The four animals brought over in the 1980s have now bred, and there are an estimated 35 living in the wild in Colombia – the largest herd outside Africa. The animals can live for up to 60 years.

And wildlife experts are concerned that they could disrupt the local ecosystem – or even kill a human. The animals will barge through fences and walls, and have been found wandering in villages 100 miles away.

A cull begun in 2009 was stopped when the death of Pepe the hippo caused outrage across the country. Costly and tricky attempts to castrate the hippos to curb their spread have not made much progress. Only four have had the snip.

It is hard to tell whether a hippo is a male because its testicles are hidden inside. If you do manage to grab a several-ton hippo before it disappears underwater, you have to put it to sleep – an expensive and dangerous procedure.